Subacute sclerosing panencephalitis (SSPE), also known as Dawson disease, is a rare chronic, progressive and fatal encephalitis that affects primarily children and young adults, caused by a persistent infection of immune resistant measles virus.
1 in 100,000 people infected with measles develop SSPE, with a latency of typically a decade (range 4-23 years) and thus a typical age of onset of 9-13 years of age 1,2. The marked decline of SSPE in first world nations is yet another example of the benefit of widespread vaccination.
Clinical presentation is gradual, progressive neuropsychological deterioration, consisting of personality change, seizures, myoclonus, ataxia, photosensitivity, ocular abnormalities, spasticity, and coma.
Histopathologically, SSPE demonstrates the same changes seen in other chronic viral cerebral infections, such as HIV encephalitis and post-infectious encephalomyelitis 2.
CSF analysis may show elevated levels of:
- anti-measles antibodies
- periodic slow-wave complexes are characteristic 4-6
Features depend on the stage of disease. In the acute setting, patchy asymmetric regions of white matter involvement are present, typically in the temporal and parietal lobes. Gradually more extensive white matter involvement develops with additional involvement of the corpus callosum and basal ganglia. Eventually, a generalised encephalomalacia develops 1 and parenchymal loss may be seen in later stages.
- T2/FLAIR: high signal within white matter in the parietal and temporal lobes in the acute stage 3
- T1 C+ (Gd): enhancement of affected regions may occur early in the course of the disease.
MR spectroscopy may demonstrate 1,3
- decreased NAA: from neuronal loss
- increases in choline: from demyelination
- increase myo-inositol: from active gliosis
- elevated lactate: from macrophagic infiltration
- 1. Sener RN. Subacute sclerosing panencephalitis findings at MR imaging, diffusion MR imaging, and proton MR spectroscopy. AJNR Am J Neuroradiol. 2004;25 (5): 892-4. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 2. Brismar J, Gascon GG, Von steyern KV et-al. Subacute sclerosing panencephalitis: evaluation with CT and MR. AJNR Am J Neuroradiol. 1996;17 (4): 761-72. AJNR Am J Neuroradiol (abstract) - Pubmed citation
- 3. Degnan AJ, Levy LM. Neuroimaging of rapidly progressive dementias, part 2: prion, inflammatory, neoplastic, and other etiologies. AJNR Am J Neuroradiol. 2014;35 (3): 424-31. doi:10.3174/ajnr.A3455 - Pubmed citation
- 4. Markand ON, Panszi JG. The electroencephalogram in subacute sclerosing panencephalitis. Archives of neurology. 32 (11): 719-26. Pubmed
- 5. Markand ON. Electroencephalography in diffuse encephalopathies. Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society. 1 (4): 357-407. Pubmed
- 6. Garg RK Subacute sclerosing panencephalitis Postgraduate Medical Journal 2002;78:63-70.